This validity of this patent has been widely challenged on the grounds that it covers an obvious invention.
CSIRO's solution may not have been so obvious at the time, quote from http://www.theaustralian.com.au/australian-it/how-csiros-stars-won-the-wifi-battle/story-e6frgakx-1226316861762
"If the problem was so unimportant, then why did 22 major research agencies around the world, including IBM, shut down their wireless research when the CSIRO published its results?"
"Ask not what A Group of Employees can do for you. But ask what can All Employees do for A Group of Employees." -- Mike Dennison